The use of an inflatable garment applied to a limb or other area of the human body as a means of enhancing blood circulation is a well established medical technique with proven clinical benefits.
Such a device, known as the A-V Impulse System® is in widespread use and is designed to apply intermittent impulses to the foot in such a manner as to mimic ambulatory movement which is known periodically to empty the veins of the foot to drive the blood throughout the body.
The A-V Impulse System® comprises an inflatable bladder being part of or integral with means in the form of a foot wrap for securing the bladder in the plantar arch of the foot and about the area to be treated.
During use the bladder is filled with a fluid such as air to expand and apply cyclical force to the plantar arch directed in such a way as to empty the plantar veins of the foot.
The bladder is held pressurized for a period before releasing the fluid and then the cycle is repeated.
The rate of filling or venting of the bladder may vary from fractions of a second to several seconds according to application, but is dependent upon the bladder volume, fluid flow rate and operating pressure.
To be effective the bladder has to be filled rapidly and the consequent high velocity flow of fluid results in the generation of noise as the fluid passes from the controlling system through the connecting tubing into the bladder.
Noise reduction may be achieved by reducing the fluid flow rate but this is not a feasible remedy because it affects the required rate of pressurization and desired operating characteristics.